# Linux # user and user group management

User Management

1. Add user
   the useradd [option] username
   default system automatically assigns primary group and the UID
   options [G, G, U]
   -g: Specifies the user's home group
   -G: about the specified user group is attached
   -u: Specifies the uid

2. Modify the user
   the usermod [options] username
   option [G, G, U, L]
   -l: modify the user name

3. Replace the user
   su (switch user) username

4. Change the user password
   passwd username

User group management

1. Adding user groups
   groupadd [options] user group names
   by default the system automatically assigns the user group id
   option [G]
   -g: Specifies the user group id

2. Modify User Group
   groupmod [Option] User group name
   option [G, n-]
   -g: Modify User Group ID
   -n: Modify User Group Name